This section introduces aspects that may be helpful to facilitating a better understanding of the inventions. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
Cables are often installed in buildings and tunnels to provide radio frequency (RF) coverage by being mounted to walls or sealing using clamps. Such cables have apertures in their outer conductor that serve as a radiating element through the aperture, such that a plurality of apertures creates an antenna array to provide wireless telecommunication services.
To help avoid interference in RF signals being transmitted by the cables, the cable clamps are often made of plastic material. To help prevent the cable from dropping from the sealing or wall in case of a fire, metal clamping structures are often placed at regular intervals instead of plastic clamps.
Metallic material in proximity to an aperture of the radiating element can generate intermodulation RF signals which can interfere with wireless telecommunication signals, thereby deteriorating the quality of the wireless phone calls or even cause dropped calls. Intermodulation RF signals are created when high power signals transmitted by the cable impact with metal clamping structures. Various factors such as non-linearity of oxide layers on the metal, the presence of ferromagnetic material, loose or moving metal-to-metal contacts, can all affect the strength of the intermodulation RF signals created and radiated by metallic clamping components and received by the cable.